Drainage, Waste & VentQuestion 26 of 120
A 4 in horizontal drain is sized to carry a load of drainage fixture units. Which pipe run carries the greatest DFU load for a given diameter?
a.A building drain sloped at 1/4 in per ft compared with the same drain at 1/8 in per ft
b.A horizontal fixture branch compared with a building drain of the same size
c.A vent stack compared with a drainage stack of the same size
d.A trap arm compared with a fixture branch of the same size
Explanation
For a horizontal drain of a given diameter, increasing the slope increases the carrying capacity, so a 4 in building drain at 1/4 in per ft is rated for more DFU than the same drain at 1/8 in per ft. A horizontal fixture branch is rated for fewer DFU than a building drain of equal size, a vent stack carries air rather than a DFU load, and a trap arm serves a single fixture.
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- A commercial kitchen has a two-compartment sink whose drain must not connect directly to the sanitary drainage system. How must it discharge?
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- A 3 in horizontal branch must gain 4-1/2 in of fall between two fixed points. At the minimum slope for 3 in pipe, what is the longest run that produces exactly that fall?
- A branch serves one water closet at 4 DFU, one lavatory at 1 DFU, one bathtub with shower at 2 DFU, and one kitchen sink at 2 DFU. What is the total DFU load on that branch?
- A horizontal fixture branch serves three lavatories only. Any branch that receives the discharge of a water closet must be at least what size?
- A 1-1/4 in trap arm serves a small lavatory. The vent is located 3 ft of developed length from the trap weir. What is the correct evaluation?
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